On a roll Achievement
On a roll0
Watched 3 related talks in a row
Related talks will appear both at the end of any talk, as well as in succession during a playlist. When you watch talks in a playlist though, the achievement will not track so this has to be done separate the playlist achievements. Here's how I would do it:
Go to 'Browse All' option, and then go to a refined topic such as 'Politics.' From here watch any video from the list, and at the end you will see related videos, so choose the next. Fast-forward through that and finally choose the last related video for the achievement to unlock.